Installing ATI Radein 1600 Pro in 4600I

Have a 266GH 4600I with the Intell Intergrated Graphics chip -have worked fine up to now-need to have a bit more bandwith on the graphics side of things - Not a real Gamer Type - the card matches the config I need. Have read the Hardware documentation & tried to figure out how to install the card - card has 1 connector to drive the fan on the card -but needs to plug into the PC Pwoer supply - there looks to be a match on the cable config for what is called the P6 connector & I am assumming that I plug the Power side connection into this available connection -not 100% sure but that looks to be the power source I need -please correct me if I am wrong -

But not sure what to do with the Data connection since I have 2 Disk Drives  - one for the OS & the other for backup data -does the grabhics card need to be connected to the drive with the OS Running on it or does it make any difference? Any guidance or suggestions would be a big help.